/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWidgets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qcommandlinkbutton.h"
#include "qstylepainter.h"
#include "qstyleoption.h"
#include "qtextdocument.h"
#include "qtextlayout.h"
#include "qcolor.h"
#include "qfont.h"
#include <qmath.h>

#include "private/qpushbutton_p.h"

QT_BEGIN_NAMESPACE

/*!
    \class QCommandLinkButton
    \since 4.4
    \brief The QCommandLinkButton widget provides a Vista style command link button.

    \ingroup basicwidgets
    \inmodule QtWidgets

    The command link is a new control that was introduced by Windows Vista. Its
    intended use is similar to that of a radio button in that it is used to choose
    between a set of mutually exclusive options. Command link buttons should not
    be used by themselves but rather as an alternative to radio buttons in
    Wizards and dialogs and makes pressing the "next" button redundant.
    The appearance is generally similar to that of a flat pushbutton, but
    it allows for a descriptive text in addition to the normal button text.
    By default it will also carry an arrow icon, indicating that pressing the
    control will open another window or page.

    \sa QPushButton, QRadioButton
*/

/*!
    \property QCommandLinkButton::description
    \brief A descriptive label to complement the button text

    Setting this property will set a descriptive text on the
    button, complementing the text label. This will usually
    be displayed in a smaller font than the primary text.
*/

/*!
    \property QCommandLinkButton::flat
    \brief This property determines whether the button is displayed as a flat
    panel or with a border.

    By default, this property is set to false.

    \sa QPushButton::flat
*/

class QCommandLinkButtonPrivate : public QPushButtonPrivate
{
    Q_DECLARE_PUBLIC(QCommandLinkButton)

public:
    QCommandLinkButtonPrivate()
        : QPushButtonPrivate(){}

    void init();
    qreal titleSize() const;
    bool usingVistaStyle() const;

    QFont titleFont() const;
    QFont descriptionFont() const;

    QRect titleRect() const;
    QRect descriptionRect() const;

    int textOffset() const;
    int descriptionOffset() const;
    int descriptionHeight(int width) const;
    QColor mergedColors(const QColor &a, const QColor &b, int value) const;

    int topMargin() const { return 10; }
    int leftMargin() const { return 7; }
    int rightMargin() const { return 4; }
    int bottomMargin() const { return 10; }

    QString description;
    QColor currentColor;
};

// Mix colors a and b with a ratio in the range [0-255]
QColor QCommandLinkButtonPrivate::mergedColors(const QColor &a, const QColor &b, int value = 50) const
{
    Q_ASSERT(value >= 0);
    Q_ASSERT(value <= 255);
    QColor tmp = a;
    tmp.setRed((tmp.red() * value) / 255 + (b.red() * (255 - value)) / 255);
    tmp.setGreen((tmp.green() * value) / 255 + (b.green() * (255 - value)) / 255);
    tmp.setBlue((tmp.blue() * value) / 255 + (b.blue() * (255 - value)) / 255);
    return tmp;
}

QFont QCommandLinkButtonPrivate::titleFont() const
{
    Q_Q(const QCommandLinkButton);
    QFont font = q->font();
    if (usingVistaStyle()) {
        font.setPointSizeF(12.0);
    } else {
        font.setBold(true);
        font.setPointSizeF(9.0);
    }

    // Note the font will be resolved against
    // QPainters font, so we need to restore the mask
    int resolve_mask = font.resolve_mask;
    QFont modifiedFont = q->font().resolve(font);
    modifiedFont.detach();
    modifiedFont.resolve_mask = resolve_mask;
    return modifiedFont;
}

QFont QCommandLinkButtonPrivate::descriptionFont() const
{
    Q_Q(const QCommandLinkButton);
    QFont font = q->font();
    font.setPointSizeF(9.0);

    // Note the font will be resolved against
    // QPainters font, so we need to restore the mask
    int resolve_mask = font.resolve_mask;
    QFont modifiedFont = q->font().resolve(font);
    modifiedFont.detach();
    modifiedFont.resolve_mask = resolve_mask;
    return modifiedFont;
}

QRect QCommandLinkButtonPrivate::titleRect() const
{
    Q_Q(const QCommandLinkButton);
    QRect r = q->rect().adjusted(textOffset(), topMargin(), -rightMargin(), 0);
    if (description.isEmpty())
    {
        QFontMetrics fm(titleFont());
        r.setTop(r.top() + qMax(0, (q->icon().actualSize(q->iconSize()).height()
                 - fm.height()) / 2));
    }

    return r;
}

QRect QCommandLinkButtonPrivate::descriptionRect() const
{
    Q_Q(const QCommandLinkButton);
    return q->rect().adjusted(textOffset(), descriptionOffset(),
                              -rightMargin(), -bottomMargin());
}

int QCommandLinkButtonPrivate::textOffset() const
{
    Q_Q(const QCommandLinkButton);
    return q->icon().actualSize(q->iconSize()).width() + leftMargin() + 6;
}

int QCommandLinkButtonPrivate::descriptionOffset() const
{
    QFontMetrics fm(titleFont());
    return topMargin() + fm.height();
}

bool QCommandLinkButtonPrivate::usingVistaStyle() const
{
    Q_Q(const QCommandLinkButton);
    //### This is a hack to detect if we are indeed running Vista style themed and not in classic
    // When we add api to query for this, we should change this implementation to use it.
    return q->style()->inherits("QWindowsVistaStyle")
        && q->style()->pixelMetric(QStyle::PM_ButtonShiftHorizontal, nullptr) == 0;
}

void QCommandLinkButtonPrivate::init()
{
    Q_Q(QCommandLinkButton);
    QPushButtonPrivate::init();
    q->setAttribute(Qt::WA_Hover);
    q->setAttribute(Qt::WA_MacShowFocusRect, false);

    QSizePolicy policy(QSizePolicy::Preferred, QSizePolicy::Preferred, QSizePolicy::PushButton);
    policy.setHeightForWidth(true);
    q->setSizePolicy(policy);

    q->setIconSize(QSize(20, 20));
    QStyleOptionButton opt;
    q->initStyleOption(&opt);
    q->setIcon(q->style()->standardIcon(QStyle::SP_CommandLink, &opt));
}

// Calculates the height of the description text based on widget width
int QCommandLinkButtonPrivate::descriptionHeight(int widgetWidth) const
{
    // Calc width of actual paragraph
    int lineWidth = widgetWidth - textOffset() - rightMargin();

    qreal descriptionheight = 0;
    if (!description.isEmpty()) {
        QTextLayout layout(description);
        layout.setFont(descriptionFont());
        layout.beginLayout();
        while (true) {
            QTextLine line = layout.createLine();
            if (!line.isValid())
                break;
            line.setLineWidth(lineWidth);
            line.setPosition(QPointF(0, descriptionheight));
            descriptionheight += line.height();
        }
        layout.endLayout();
    }
    return qCeil(descriptionheight);
}

/*!
    \reimp
 */
QSize QCommandLinkButton::minimumSizeHint() const
{
    Q_D(const QCommandLinkButton);
    QSize size = sizeHint();
    int minimumHeight = qMax(d->descriptionOffset() + d->bottomMargin(),
                             icon().actualSize(iconSize()).height() + d->topMargin());
    size.setHeight(minimumHeight);
    return size;
}

/*!
    Constructs a command link with no text and a \a parent.
*/

QCommandLinkButton::QCommandLinkButton(QWidget *parent)
: QPushButton(*new QCommandLinkButtonPrivate, parent)
{
    Q_D(QCommandLinkButton);
    d->commandLink = true;
    d->init();
}

/*!
    Constructs a command link with the parent \a parent and the text \a
    text.
*/

QCommandLinkButton::QCommandLinkButton(const QString &text, QWidget *parent)
    : QCommandLinkButton(parent)
{
    setText(text);
}

/*!
    Constructs a command link with a \a text, a \a description, and a \a parent.
*/
QCommandLinkButton::QCommandLinkButton(const QString &text, const QString &description, QWidget *parent)
    : QCommandLinkButton(text, parent)
{
    setDescription(description);
}

/*!
    Destructor.
*/
QCommandLinkButton::~QCommandLinkButton()
{
}

/*! \reimp */
bool QCommandLinkButton::event(QEvent *e)
{
    return QPushButton::event(e);
}

/*! \reimp */
QSize QCommandLinkButton::sizeHint() const
{
//  Standard size hints from UI specs
//  Without note: 135, 41
//  With note: 135, 60
    Q_D(const QCommandLinkButton);

    QSize size = QPushButton::sizeHint();
    QFontMetrics fm(d->titleFont());
    int textWidth = qMax(fm.horizontalAdvance(text()), 135);
    int buttonWidth = textWidth + d->textOffset() + d->rightMargin();
    int heightWithoutDescription = d->descriptionOffset() + d->bottomMargin();

    size.setWidth(qMax(size.width(), buttonWidth));
    size.setHeight(qMax(d->description.isEmpty() ? 41 : 60,
                        heightWithoutDescription + d->descriptionHeight(buttonWidth)));
    return size;
}

/*! \reimp */
int QCommandLinkButton::heightForWidth(int width) const
{
    Q_D(const QCommandLinkButton);
    int heightWithoutDescription = d->descriptionOffset() + d->bottomMargin();
    // find the width available for the description area
    return qMax(heightWithoutDescription + d->descriptionHeight(width),
                icon().actualSize(iconSize()).height() + d->topMargin() +
                d->bottomMargin());
}

/*! \reimp */
void QCommandLinkButton::paintEvent(QPaintEvent *)
{
    Q_D(QCommandLinkButton);
    QStylePainter p(this);
    p.save();

    QStyleOptionButton option;
    initStyleOption(&option);

    //Enable command link appearance on Vista
    option.features |= QStyleOptionButton::CommandLinkButton;
    option.text = QString();
    option.icon = QIcon(); //we draw this ourselves
    QSize pixmapSize = icon().actualSize(iconSize());

    const int vOffset = isDown()
        ? style()->pixelMetric(QStyle::PM_ButtonShiftVertical, &option) : 0;
    const int hOffset = isDown()
        ? style()->pixelMetric(QStyle::PM_ButtonShiftHorizontal, &option) : 0;

    //Draw icon
    p.drawControl(QStyle::CE_PushButton, option);
    if (!icon().isNull())
        p.drawPixmap(d->leftMargin() + hOffset, d->topMargin() + vOffset,
        icon().pixmap(pixmapSize, isEnabled() ? QIcon::Normal : QIcon::Disabled,
                                  isChecked() ? QIcon::On : QIcon::Off));

    //Draw title
    QColor textColor = palette().buttonText().color();
    if (isEnabled() && d->usingVistaStyle()) {
        textColor = QColor(21, 28, 85);
        if (underMouse() && !isDown())
            textColor = QColor(7, 64, 229);
        //A simple text color transition
        d->currentColor = d->mergedColors(textColor, d->currentColor, 60);
        option.palette.setColor(QPalette::ButtonText, d->currentColor);
    }

    int textflags = Qt::TextShowMnemonic;
    if (!style()->styleHint(QStyle::SH_UnderlineShortcut, &option, this))
        textflags |= Qt::TextHideMnemonic;

    p.setFont(d->titleFont());
    p.drawItemText(d->titleRect().translated(hOffset, vOffset),
                    textflags, option.palette, isEnabled(), text(), QPalette::ButtonText);

    //Draw description
    textflags |= Qt::TextWordWrap | Qt::ElideRight;
    p.setFont(d->descriptionFont());
    p.drawItemText(d->descriptionRect().translated(hOffset, vOffset), textflags,
                    option.palette, isEnabled(), description(), QPalette::ButtonText);
    p.restore();
}

void QCommandLinkButton::setDescription(const QString &description)
{
    Q_D(QCommandLinkButton);
    d->description = description;
    updateGeometry();
    update();
}

QString QCommandLinkButton::description() const
{
    Q_D(const QCommandLinkButton);
    return d->description;
}

QT_END_NAMESPACE

#include "moc_qcommandlinkbutton.cpp"
